Role of pre-coagulation in ultralow pressure membrane system for Microcystis aeruginosa-laden water treatment: Membrane fouling potential and mechanism

This work systematically studied the role of pre-coagulation in the performance of ultralow pressure membrane system for algae-laden water treatment. The membrane performance with/without pre-coagulation was compared in terms of membrane permeate flux, water quality and membrane fouling. Ultralow pressure membrane system can effectively reduce TOC of Microcystis aertiginosa-laden water from 5.8 to 2.1 mg/L, and pre-coagulation removed most large inorganic particles but few small organic particles. Interestingly, pre-coagulation aggravated the fouling of ultralow membrane system which is generally acknowledged method to alleviate the ultrafiltration membrane fouling. According to Extended Derjaguin-Landau-Verwey-Overbeek theory (XDLVO), the interaction energy of membrane-foulants (Delta G(fmTOT) = -41.95 mJ/m(2)), and foulant-foulant (Delta G(fmTOT)= -30.15 mJ/m(2)) with coagulation were higher than those without coagulation Delta G(fmTOT) = -3654 mJ/m(2)) and (Delta G(fmTOT) = -15.73 mJ/m(2)) suggesting greater adherence between membrane and foulants & foulant and foulant after coagulation, which well agreed with SEM results. Membrane fouling models were also applied to analyze the fouling mechanism of ultralow-pressure membrane filtration. Based on above analysis, the possible fouling mechanisms for membrane filtration with/without precoagulation were proposed and then confirmed by pre-filtration experiment, where large inorganic particles played important roles.Our study could be indicative for membrane fouling control of ultralow-pressure membrane filtration for the treatment of algae-laden water. (C) 2019 Published by Elsevier B.V.